Candesartan is a potent, long-acting, selective AT1 subtype angiotensin II receptor antagonist. Candesartan meets the requirement of high potency but it is poorly absorbed by the body when administered orally. To overcome the poor absorption, the prodrug candesartan cilexetil was developed. During absorption in the gastrointestinal tract candesartan cilexetil is rapidly and completely hydrolyzed to candesartan. The chemical name for candesartan is: 2-ethoxy-1-[[2′-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-1H-benzimidazole-7-carboxylic acid. The chemical name for candesartan cilexetil is (±)-1-[[(cyclohexyloxy)carbonyl]oxy]ethyl-2-ethoxy-1-[[2′-(1H-tetrazol-5-yl) 1,1′biphenyl-4-yl]methyl]-1H-benzimidazole-7-carboxylate. Candesartan cilexetil is a white to off-white powder and is sparingly soluble in water and in methanol. Although candesartan cilexetil contains an asymmetric center in the ester portion of the molecule, candesartan cilexetil is sold as the racemic mixture.

Angiotensin II is formed from angiotensin I in a reaction catalyzed by angiotensin-converting enzyme (ACE, kininase II). Angiotensin II is the principal pressor agent of the renin-angiotensin system, with effects that include vasoconstriction, stimulation of synthesis and release of aldosterone, cardiac stimulation, and renal reabsorption of sodium. Angiotensin II helps maintain constant blood pressure despite fluctuations in a person's state of hydration, sodium intake and other physiological variables. Angiotensin II also performs regulatory tasks such as inhibiting excretion of sodium by the kidneys, inhibiting norephedrin reuptake, and stimulating aldosterone biosynthesis. Candesartan blocks the vasoconstrictor and aldosterone secreting effects of angiotensin II by selectively blocking the binding of angiotensin II to the AT1 receptor in many tissues, such as vascular smooth muscle and the adrenal gland. By inhibiting angiotensin II binding to AT1 receptors, candesartan disrupts the vasoconstriction mediated by AT1 receptors. Blocking vasoconstriction by angiotensin II has been found to be beneficial to patients with hypertension. The United States Food and Drug Administration has approved candesartan for the treatment of hypertension alone or in combination with other antihypertensive agents.
U.S. Pat. No. 5,196,444 discloses working Example 7, 1-[[(cyclohexyloxy)carbonyl]oxy]ethyl-2-ethoxy-1-[[2′-(1H-tetrazol-5-yl) 1,1′biphenyl-4-yl]methyl]-1H-benzimidazole-7-carboxylate was formed by reacting 2-ethoxy-1-[[2′-(N-triphenylmethyltetrazol-5-yl)biphenyl-4-yl]methyl]benzimidazole-7-carboxylic acid in DMF with cyclohexyl-1-iodoethyl carbonate to form cilexetil trityl candesartan and deprotecting with a methanolic hydrochloric acid to form candesartan cilexetil.
U.S. Pat. No. 5,578,733, discloses the deprotection of cilexetil trityl candesartan using mineral acids under substantially anhydrous conditions.